1. Field of the Invention
The present invention relates generally to a television receiver having a display screen with a wide aspect ratio of 16 to 9 and, more particularly, to such a television receiver that can display a video image having a 4 to 3 aspect ratio.
2. Description of the Related Art
A television receiver having a display screen with the wide aspect ratio of 16 to 9 has been put into practical use. When displaying a video signal conformed to a standard aspect ratio of 4 to 3 on a display screen of such a television receiver, the conventional approaches have resulted in displays such as shown in FIGS. 6A to 6C. That is, in the approach resulting in the display of FIG. 6A, portions where no video image is displayed are formed at the right and left ends of the display screen. In the approach resulting in the display of FIG. 6B, the display of the video signal is expanded such that a horizontal width of the 4 to 3 aspect ratio video image coincides with the horizontal width of the 16 to 9 aspect ratio display screen.
According to the displaying method corresponding to FIG. 6A, however, the portions where no video image is displayed at the right and left ends of the display screen are a disadvantage to the viewer. According to the displaying method of FIG. 6B, the upper and lower portions of the video image based on the video signal to be displayed on the display screen are cut off and not seen, so that the viewer is again disadvantaged because he can not see all the video image present in the video signal.
Further, as shown in FIG. 6C, there has been proposed another display approach intended as a improvement over the approach of FIG. 6A in which the video image based on the 4 to 3 aspect ratio video signal is expanded in the horizontal direction, so that the video image based on the 4 to 3 aspect ratio video signal coincides with the horizontal and vertical widths of the 16 to 9 aspect ratio display screen. Nevertheless, according to this display method, since the video image on the display screen is compressed in the vertical direction, the visual image looks very unnatural. This system is described in published EP Patent Application 0,551,168, for example.
In contrast to the aforesaid various displaying methods, there has been proposed still another displaying method resulting in the screen shown in FIG. 7A. In this method, as shown by FIG. 7B representing a conceptual drawing of FIG. 7A, only portions in the vicinity of the right and left ends of the video image on the screen are expanded in the horizontal direction. According to this method, a viewer can see the video image on the screen with little unnatural feeling, because the video image can be displayed naturally at the center portion of the display screen. In addition, the viewer's visual recognition of the video image becomes weaker at the vicinity of the right and left ends when the viewer looks at the center portion of the display screen.
When such a display is performed on the screen, however, if the video image based on the video signal moves to the right or to the left, the moving speed of the video image becomes uneven. As a consequence, a viewer feels very unnatural when watching such a moving image. That is, when such a display is performed on the screen, a viewer can see the video image with little unnatural feeling if the view point of the viewer on the screen is fixed, however, the viewer feels very unnatural as the viewer moves his view point to the right or left.
According to an investigation that has been performed as to the number of movements of the viewer's view point when the viewer views various kinds of programs found in general television broadcasting, it has been proved, as shown by the table of FIG. 8, that the number of movements of view point in the vertical direction is much less by a factor of two to five than the number of movements in the horizontal direction. The present invention has been made in view of this disparity between changes in horizontal and vertical points of view found in general television program material.
A problem to be solved by the present invention is that, according to each of the previously proposed displaying methods as described above, when displaying the video image of the video signal with the standard aspect ratio of 4 to 3 on the display screen with the wide aspect ratio of 16 to 9, there is a fear that the viewer will likely feel the displayed visual image to be unnatural.